/*
 *  linux/fs/pipe.c
 *
 *  (C) 1991  Linus Torvalds
 */

#include <signal.h>

#include <linux/sched.h>
#include <linux/mm.h> /* for get_free_page */
#include <asm/segment.h>

int read_pipe(struct m_inode *inode, char *buf, int count) {
    int chars, size, read = 0;

    while (count > 0) {
        while (!(size = PIPE_SIZE(*inode))) {
            wake_up(&inode->i_wait);
            if (inode->i_count != 2) /* are there any writers? */
                return read;
            sleep_on(&inode->i_wait);
        }
        chars = PAGE_SIZE - PIPE_TAIL(*inode);
        if (chars > count)
            chars = count;
        if (chars > size)
            chars = size;
        count -= chars;
        read += chars;
        size = PIPE_TAIL(*inode);
        PIPE_TAIL(*inode) += chars;
        PIPE_TAIL(*inode) &= (PAGE_SIZE - 1);
        while (chars-- > 0)
            put_fs_byte(((char *)inode->i_size)[size++], buf++);
    }
    wake_up(&inode->i_wait);
    return read;
}

int write_pipe(struct m_inode *inode, char *buf, int count) {
    int chars, size, written = 0;

    while (count > 0) {
        while (!(size = (PAGE_SIZE - 1) - PIPE_SIZE(*inode))) {
            wake_up(&inode->i_wait);
            if (inode->i_count != 2) { /* no readers */
                current->signal |= (1 << (SIGPIPE - 1));
                return written ? written : -1;
            }
            sleep_on(&inode->i_wait);
        }
        chars = PAGE_SIZE - PIPE_HEAD(*inode);
        if (chars > count)
            chars = count;
        if (chars > size)
            chars = size;
        count -= chars;
        written += chars;
        size = PIPE_HEAD(*inode);
        PIPE_HEAD(*inode) += chars;
        PIPE_HEAD(*inode) &= (PAGE_SIZE - 1);
        while (chars-- > 0)
            ((char *)inode->i_size)[size++] = get_fs_byte(buf++);
    }
    wake_up(&inode->i_wait);
    return written;
}

int sys_pipe(unsigned long *fildes) {
    struct m_inode *inode;
    struct file *f[2];
    int fd[2];
    int i, j;

    j = 0;
    for (i = 0; j < 2 && i < NR_FILE; i++)
        if (!file_table[i].f_count)
            (f[j++] = i + file_table)->f_count++;
    if (j == 1)
        f[0]->f_count = 0;
    if (j < 2)
        return -1;
    j = 0;
    for (i = 0; j < 2 && i < NR_OPEN; i++)
        if (!current->filp[i]) {
            current->filp[fd[j] = i] = f[j];
            j++;
        }
    if (j == 1)
        current->filp[fd[0]] = NULL;
    if (j < 2) {
        f[0]->f_count = f[1]->f_count = 0;
        return -1;
    }
    if (!(inode = get_pipe_inode())) {
        current->filp[fd[0]] =
            current->filp[fd[1]] = NULL;
        f[0]->f_count = f[1]->f_count = 0;
        return -1;
    }
    f[0]->f_inode = f[1]->f_inode = inode;
    f[0]->f_pos = f[1]->f_pos = 0;
    f[0]->f_mode = 1; /* read */
    f[1]->f_mode = 2; /* write */
    put_fs_long(fd[0], 0 + fildes);
    put_fs_long(fd[1], 1 + fildes);
    return 0;
}
